The present invention relates to a key locator for an electronic key system that determines the location of an electronic key.
In the prior art, an electronic key transmits an ID code to a vehicle through wireless communication, and the vehicle verifies the ID code. One example of an electronic key system is a key-operation-free system. In a key-operation-free system, a vehicle transmits an ID code response request signal through wireless communication. In response to the request signal, an electronic key returns an ID code, and the vehicle verifies the received ID code. A key-operation-free system may include a smart entry system and a one-push engine-start system. A smart entry system enables doors to be locked or unlocked when an ID code received from an electronic key located outside the vehicle is verified. A one-push engine-start system enables the starting of the engine when an engine switch button is pushed in the vehicle after verification of an ID code received from the electronic key, which is located inside the vehicle.
FIG. 9 illustrates an example of an electronic key system installed in a vehicle 80 having doors 81 and 82. The electronic key system includes antennas 83 and 84, which are respectively arranged in the doors 81 and 82, and an electronic key 85, which responds to radio signals transmitted from the antennas 83 and 84. The transmission range of the radio signal transmitted from the antenna 83 defines a driver side antenna area 86. The transmission range of the radio signal transmitted from the antenna 84 defines a passenger side antenna area 87. In the vehicle 80, the driver side antenna 83, which is arranged near the driver side door 81, and the passenger side antenna 84, which is arranged near the passenger side door 82, sequentially transmit a request signal. Based on whether the electronic key 85 returns an ID code in response to the request signal (logic determination of response status), the vehicle 80 determines the key location (refer to Japanese Laid-Open Patent Publication Nos. 2004-84406 and 2005-76329).
For example, when the electronic key 85 responds to a request signal from the driver side antenna 83 but not to the request signal from the passenger side antenna 84, the vehicle 80 determines that the electronic key 85 is located outside the vehicle 80. Further, when the electronic key 85 responds to a request signal from the passenger side antenna 84 but not to the request signal from the driver side antenna 83, the vehicle 80 determines that the electronic key 85 is located outside the vehicle 80. When the electronic key 85 responds to the request signals from both of the driver side antenna 83 and the passenger side antenna 84, the vehicle 80 determines that the electronic key 85 is located inside the vehicle 80.
Normally, a single master key and one or more sub-keys are registered with a single vehicle 80. Thus, as shown in the state of FIG. 10, one of the plurality of electronic keys 85 may be located outside the driver side of the vehicle 80, while another is located outside the passenger side of the vehicle 80. However, in the prior art, the key location is determined based on the logic determination of the response status. Thus, the state shown in FIG. 10 results in an erroneous determination that an electronic key 85 is located inside the vehicle 80.
FIG. 11 shows a state in which electronic keys 85a, 85b, and 85c are present outside the driver side and passenger side of the vehicle 80 and inside the vehicle 80 at the same time. There are cases in which the antennas 83 and 84 transmit request signals in order of priority to electronic keys. In such a case, when an electronic key responds to a request signal sent from an antenna, that antenna would not transmit subsequent request signals to electronic keys having lower priority. For example, when the order of priority is such that the electronic key 85a is ranked first, the electronic key 85b is second, and the electronic key 85c is third, once the electronic key 85a responds to a request signal from the driver side antenna 83, the driver side antenna 83 would stop transmitting subsequent request signals. The electronic key 85a, which is located outside the passenger side antenna area 87, would not respond to a request signal from the passenger side antenna 84. However, the electronic key 85b, which is second in order of priority, would respond to a request signal from the passenger side antenna 84. This would stop transmission of subsequent request signals from the passenger side antenna 84. As a result, the vehicle 80 would not be able to recognize the electronic key 85c that is located inside the vehicle 80.
The present invention provides a device that accurately determines the location of the electronic key.
One aspect of the present invention is a key locator for an electronic key system. The key locator has a plurality of antennas arranged in a key communication subject and including a first antenna and a second antenna. The first and second antennas each form a communication area, with the communication area of the first antenna partially overlapping the communication area of the second antenna and thereby forming an overlapping communication area. The communication areas of the first and second antennas each include a non-overlapping communication area. A first query unit sends a first query from the first antenna to each of a plurality of electronic keys registered with the key communication subject. A second query unit sends a second query from the second antenna to only an electronic key that responds to the first query. A key locating unit determines the location of the electronic key in accordance with whether or not a response to the first query and the second query is received from the electronic key.
A further aspect of the present invention is an electronic key system for a vehicle. The electronic key system includes a plurality of electronic keys for the vehicle and a key locator, which is capable of performing wireless communication with the electronic keys. The key locator includes a first antenna and a second antenna capable of performing wireless communication with the electronic keys. The first and second antennas each form a communication area, with the communication area of the first antenna partially overlapping the communication area of the second antenna and thereby forming an overlapping communication area inside the vehicle. The communication areas of the first and second antennas each include a non-overlapping communication area formed at least outside the vehicle. A first query unit transmits a first query to the communication area of the first antenna from the first antenna. A second query unit transmits a second query to the communication area of the second antenna from the second antenna after the first query. The second query is generated such that the second query is correctly processed and responded to only by the electronic key that responds to the first query. A key locating unit determines whether or not there is an electronic key located inside the vehicle and whether or not there is an electronic key located outside the vehicle in accordance with whether or not a response to the first query and a response to the second query are received from the electronic key.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.